January 6, 2015

# Why is Surpac so dogmatic about validation of solid models?

To understand GEOVIA Surpac’s approach to validation of solid models, it’s necessary…
Kim Ferguson-Thomas

To understand GEOVIA Surpac’s approach to validation of solid models, it’s necessary to first understand what solid models are used for by geologists, surveyors or mining engineers.

At the core of solid modeling, people use them for a few reasons:

1. To model the physical shape of some measured or designed structure.
2. To calculate the volume inside a closed structure, a stope, geological solid, tunnel, etc.
3. To use as a geometric constraint against a block model to calculate the grade of mineral content in a structure.

If the shape is the only thing being modeled, then validation is much less important, and it can often be ignored. While validation is not important for item 1, above, it is absolutely critical for accurate results for items 2 & 3. But, why is this so important?

Calculating the volume of a solid is achieved through a remarkably simple algorithm. This algorithm sums the volume underneath each and every triangle in the solid. When the solid complies with ALL of Surpac’s validation criteria, some triangles have a positive volume beneath them, while others have a negative volume beneath them. The summing of these volumes produces the net volume of the solid.

Using a solid as a geometric constraint for a block model ultimately relies on a test to determine if a point is inside or outside the solid. The algorithm that does this also requires that the solid complies with all of Surpac’s validation criteria.

Regardless of if the solid is having its volume calculated or it is being used for a block model constraint, if the solid is not valid, errors will result. The magnitude of the errors could range from unnoticeably small to enormous. Regardless of the magnitude, if the results can’t be trusted, then you are in trouble, quite possibly an enormous amount!

Surpac’s solid validation rules are there to keep you from stepping into a troublesome mess.

To help create valid solids, Surpac has a number of items on the Solids Validation menu – the most important being:

• Validate object/trisolation displays the validate objects and trisolations form for when you want to try Surpac automated tools for fixing the problems that make your solid invalid.
• Solids Repair displays the solids repair panel when the job of making your solids valid is much more complicated.

Looking for more Surpac Tips & Tricks? Check out Using Surpac’s Digitser Edge Follow Mode.

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